When a sewer backs up, the "low man on the totem pole" will flood first, then as the water level in his basement rises, the next lower house will start to fill up. It is strictly a matter of elevation. I once had a customer whose finished lower level started to flood about Midnight. After some diagnosis, I decided it was a city problem and called the emergency number. We finally determined that a manhole which was buried under the blacktop was the part of the solution because there was about a square mile of sewer backed up. My customer was one of the few with a basement in the area, and also the lowest house. IF the city had not removed the stoppage, my customer would have been the recipient of ALL the water used for showers and sinks in the area the next morning. After chopping out the blacktop and beating on the manhole cover to loosen it, a "million" cockroaches came scurrying out of the manhole and we jumped up on our trucks to let them go by.

For those familar with camera inspections......is it just that * a inspection camera* that tells how far out it goes.

So I've started doing a little survey of house and there are some houses on the block that have nil-no water backup.
Others, much worse that I. Some are just like mine ....
I thought my checkvalve install was the end all-be all, but that does not appear to be the case.

Just looking to do some homework before I schedule for a camera inspection..

It is a camera inserted into the drain line. It should show the condition of the pipe, and if they have the proper equipment, they can also trace the path of the sewer pipe, but that is a secondary function of the camera and requires that it have the transmitter in it. I cannot imagine anything that a camera could find which would relate to your sewer backup. The ones with more water were lower than you, and the ones with less were higher. The backwater valve was only HALF of the solution, but your installer did not do the second step. A pump would NEVER control the water in a house without the valve, but it would be able to keep up with water working its way through the vavle.

I've yet to get around to opening the cover on the checkvalve to check the door...

Finally got some time to speak to the plumber. We discussed camera inspections, which he felt was not needed / nor would be any remedy to the problem.
I suggested possibly putting a gate valve in the *line* behind the checkvalve and he made a good point, it's only good if you are home to operate it.
I was advised it's good practice to open the cover and just make sure there are no restrictions every 4 months or whenever a (huge storm) is to be expected.

I did check the door operation about 2 months ago or so....
It would be interesting to know at this current state, is the door down or is there something that is restricting it from actually being Fully Closed

It is a camera inserted into the drain line. It should show the condition of the pipe, and if they have the proper equipment, they can also trace the path of the sewer pipe, but that is a secondary function of the camera and requires that it have the transmitter in it. I cannot imagine anything that a camera could find which would relate to your sewer backup. The ones with more water were lower than you, and the ones with less were higher. The backwater valve was only HALF of the solution, but your installer did not do the second step. A pump would NEVER control the water in a house without the valve, but it would be able to keep up with water working its way through the vavle.

OK. The verdict is in. There was feces/and a small wad of TP blocking the door.

A wild guesstimate but I would say the checkvalve was installed around October of last year. Fast forward to June/July of 2012.
After a long stretch of renovation, I decided to remove the cover to see the checkvalve in action, and found the same issue...feces/wad of paper obstructing the door.

Just short of doing cover removals in the months of April, June, Sept, Oct......(heavy rain month periods) ---- is there anything else you might suggest.
And or running a small jetter but it's just the same amount of work to remove the cover....and confirm there are no obstructions.